The present invention relates to a filmy piezoelectric/electrostrictive element, a piezoelectric/electrostrictive device having movable portions that are operated based on a displacing operation of the piezoelectric/electrostrictive element, and a production method thereof. Specifically, the present invention relates to a piezoelectric/electrostrictive element that is excellent in temperature characteristic to enable a displacement control with high accuracy at high temperatures, and that is not subjected to deterioration even at high temperature and high humidity thereby to enable realization of a stable displacing operation over a long term, and further relates to a piezoelectric/electrostrictive device provided with the piezoelectric/electrostrictive element, and a production method thereof.
In recent years, in the fields of optical and precision apparatuses, semiconductor production, and so on, there has been a demand for displacement control elements that adjust optical path lengths, positions, etc. in the order of submicrons. In response thereto, there have been developed piezoelectric/electrostrictive elements that utilize distortion caused by an inverse piezoelectric effect or an electrostrictive effect generated upon applying an electric field to a ferroelectric body or antiferroelectric body. These displacement control elements utilizing the electric field induced distortion have features that it is easy to execute a small displacement control as compared with a conventional electromagnetic technique using servomotors, pulse motors, etc., the mechanical/electrical energy conversion efficiency is high so that power saving may be achieved, ultra-precise mounting is made possible, reduction in size and weight of the product can be achieved, and so on. Therefore, it is expected that application fields will be expanded steadily.
As such a displacement control element, for example, JP-A-10-136665 discloses a piezoelectric actuator wherein, as shown in FIG. 11, a plate-like member 200 made of a piezoelectric/electrostrictive material is provided with a hole portion 202, and a fixing portion 204, a movable portion 206, and beam portions 208 supporting them are formed integral with each other, and further, an electrode layer 210 is provided on the beam portion 208.
In this piezoelectric actuator, when an voltage is applied to the electrode layer 210, the beam portion 208 is extended/contracted in a direction of connecting the fixing portion 204 and the movable portion 206, so that it is possible to cause the movable portion 206 to perform arc-shaped displacement or rotational displacement in the plane of the plate-like member 200.
However, in the piezoelectric actuator disclosed in JP-A-10-136665, since the displacement in the extending/contracting direction of the piezoelectric/electrostrictive material (i.e. in-plane direction of the plate-like member 200) is transmitted to the movable portion 206 as it is, there has been a problem that an operation amount of the movable portion 206 is small. Further, since the piezoelectric actuator is entirely formed of the piezoelectric/electrostrictive material that is fragile and relatively heavy, it is low in mechanical strength, and inferior in handleability, impact resistance, and moisture resistance and, in addition, the piezoelectric actuator itself is heavy so that there has been a problem that it is susceptible to influence of harmful vibration (e.g. residual vibration or noise vibration upon high-speed operation) upon operation.
We have newly developed a piezoelectric/electrostrictive device provided with movable portions that are operated based on a displacing operation of a piezoelectric/electrostrictive element being a displacement control element, and proposed in JP-A-2001-320103 along with its production method, thereby to solve the aforementioned problem. This piezoelectric/electrostrictive device comprises a pair of mutually confronting thin plate portions and a fixing portion supporting these thin plate portions, wherein movable portions are provided at tip end portions of the pair of thin plate portions, and one or more piezoelectric/electro-strictive elements are disposed on at least one of the pair of thin plate portions, and is characterized in that the movable portions have mutually confronting end surfaces, and a distance between the end surfaces is greater than a length of the movable portion.